1. Field of the Invention
The invention relates to organopolysiloxane gels, methods of production thereof, and application thereof in cosmetic formulations.
2. Description of the Related Art
The organopolysiloxane gels of the present invention are produced by crosslinking an unsaturated organopolysiloxane resin with a special Si—H-containing organopolysiloxane, also called Si—H-functional crosslinking agent, in the presence of a diluent.
Crosslinked materials are polymer chains linked together in a three-dimensional network. They can be regarded as long-chain branchings, which are so numerous that a continuous, insoluble network or gel is formed.
Organopolysiloxane networks are often produced in platinum-catalyzed hydrosilylation reactions. Often a Si—H-containing organopolysiloxane and a vinyl-functional organopolysiloxane are reacted together. An essential precondition for the formation of a three-dimensional network is that at least one of the two components, the Si—H-containing organopolysiloxane or the vinyl-functional organopolysiloxane, has more than two functionalities per molecule in its average composition.
The platinum-catalyzed hydrosilylation reaction has the advantage that no by-products are formed in the formation of organopolysiloxane networks, and that linkage points and network architecture are narrowly defined. The most important reason for using organopolysiloxane gels in cosmetic applications is the resultant sensory advantages, especially the improved feel of cosmetic formulations on the skin. Furthermore, organopolysiloxane gels are used as thickening agents in cosmetic formulations.
U.S. Pat. No. 6,423,322 B1 discloses organopolysiloxane gels, which can be easily produced by a hydrosilylation reaction of a special, vinyl-functional MQ resin with a highly Si—H-containing organopolysiloxane with about 0.5 wt. % of silicon-bonded hydrogen atoms in the presence of decamethylcyclopentasiloxane as diluent, and a small amount of platinum hydrosilylation catalyst. The resultant gels are nonstringy and can be easily homogenized to a stable cream or paste. However, a substantial drawback of these organopolysiloxane gels is the resultant feel on the skin, which is not ideal for cosmetic applications.
Furthermore, as is the case with many organic diluents that are often used in cosmetic applications, suitable gels cannot be produced if an Si—H-containing organopolysiloxane with comparatively high content of silicon-bonded hydrogen atoms is used as Si—H-functional crosslinking agent. Therefore, the sometimes low compatibility of the gels with organic compounds and diluents is a disadvantage in the production of cosmetic formulations. Owing to the relatively high proportion of vinyl-functional MQ resin, such gels are also comparatively expensive to produce.
US 2004/0105828 A1 and US 2003/0095935 A1 describe a number of different silicone gels, including gels that are obtained by a hydrosilylation reaction of a Si—H-containing polysiloxane and an unsaturated MQ resin in a diluent. Improved transfer resistance is cited as an important advantage. However, there are no examples in which the production and the action of these organopolysiloxane gels are demonstrated.
The problem was to provide new organopolysiloxane gels with improved properties, in particular with an improved feel on the skin, which do not have the aforementioned disadvantages.